User Guide 035
ISL78171EVAL1Z Evaluation Board User Guide
Description
This quick start guide pertains to the ISL78171EVAL1Z
Evaluation Board. This board is populated with 60 LEDs in
6P10S (six parallel strings, each string consisting of 10 LEDs in
series) configuration to simplify evaluation and testing. The
device can function with or without an I
2
C controller. If it is
required to use I
2
C control for the ISL78171EVAL1Z board, use
a generic I
2
C interface adapter (not supplied with the
evaluation board kit) for the purpose of communication.
Please note that the slave address on the
ISL78171
is
hexadecimal 58. Please refer to the quick setup guides for
jumper settings and power-up instructions.
Key Features
• Integrated 40V boost converter
• 6 Precision current sinks, up to 50mA each
• Current matching ±0.7% typical
• Dimming modes: DC, internal PWM, direct PWM,
DC + Int/Dir PWM
• Typical dimming ratio exceeding 60,000:1 for DC + Int/Dir
PWM
• Phase shift control for internal PWM dimming
• 600kHz/800kHz/1.2MHz I
2
C selectable switching
frequency
• Dynamic headroom control
Specifications
This board has been configured and optimized for the following
operating conditions:
• Input voltage: 4.5V to 26.5V
• Output voltage: 32V typical and 40V max
• LED string current 20mA typical
References
ISL78171
Datasheet
Ordering Information
PART NUMBER
ISL78171EVAL1Z
DESCRIPTION
ISL78171 Evaluation Board
PCB Details
Board dimension = 5.525x2.550inch
Number of layers = 2
Type = FR4
Copper thickness = 2oz
FIGURE 1. ISL78171EVAL1Z FRONT SIDE
June 15, 2015
UG035.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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User Guide 035
Recommended Equipment
The following equipment is recommended to perform testing:
• 0V to 30V power supply with 5A source current capability
• Digital Multimeters (DMMs)
• 500MHz quad-trace oscilloscope
• Signal generator for PWM pins
12. For I
2
C/SMBUS and DPST mode, in order to enable the board,
write a hex 58 for slave address and write a hex 05 to register
01.
13. For DPST mode I
2
C dimming, write hex 01 to register 01 (see
data sheet for more details).
14. For DPST mode with PWM dimming, write hex 03 to register
01. This will allow PWM dimming in DPST mode.
TABLE 1. LED STRINGS CONFIGURATIONS WITH DIFFERENT JUMPER
SETTINGS
LED CONFIGUATRION
J6
J8
J11
J14
J17
JJ20
J30
J10
J13
J16
J19
J22
J24
J9
J12
J15
J18
J21
J23
Open
Open
Short
Open
Short
Open
Short
6P10S
6P9S
Short
6P8S
Quick Setup Guide (Non I
2
C)
1. Ensure that the circuit is correctly connected to the supply.
2. Connect the VIN+ supply to both J1 = BOOST-VIN and
TP9 = VIN_IN.
3. OPEN: Jumpers JP1, JP9, J9, J10, J12, J13, J15, J16, J18, J19,
J21, J22, J24, J25, J26, J27 and J28.
4. CLOSE: Jumpers JP1A:1-2, JP2A:2-3, JP3A:2-3, JP4A:2-3,
JP5A:2-3, J6, J8, J11, J14, J17, J20, J29, J30 and J31.
5. Apply 200Hz, 0-5V, 50% duty, square wave to TP13.
6. Measure the voltage between J4 and J5. IT should read ~32V
7. Note that the 6P10S LED strings are ON.
8. Apply 5V to TP13 and trim RA1 to set the LED current in CH0
to measure 20mA using a DMM in series with J8.
9. Apply a square wave of 200Hz, 5V and vary the duty from 0%
to 100% and check that the LED varies from OFF to 100%
brightness.
10. Check that the current in J8 in step 9 varies from ~0mA to
20mA. Test complete turn OFF supplies.
Quick Setup Guide (I
2
C)
1. Ensure that the circuit is correctly connected to the supply.
2. Connect the VIN+ supply to both J1 = BOOST-VIN and
TP9 = VIN_IN.
3. OPEN: Jumpers JP1, JP9, J9, J10, J12, J13, J15, J16, J18, J19,
J21, J22, J24, J25, J26, J27, J28 and J29.
4. CLOSE: Jumper JP1A:1-2, JP2A:2-3, JP3A:2-3, JP4A:1-2,
JP5A:1-2, J6, J8, J11, J14, J17, J20, J30 and J31.
5. Connect an I
2
C controller bus to either J7 or J39.
6. Set device address to 0x58.
7. IC enable is shorted to VIN by connecting jumper JP2A:2-3, so
that the EN is driven by TP9.
8. VLOGIC level for I
2
C can be generated from VDC by
connecting jumper JP3A:2-3. VLOGIC can be driven from TP7
(VLOGIC) by shorting jumper JP3A:1-2.
9. The configuration of VIN (JP1A), EN (JP2A) and VLOGIC (JP3A)
can be quickly found by referring to the table printed on the
bottom of the evaluation board, as shown in
Figure 6 on
page 7.
10. There are 4 different operation modes for ISL78171. The
setting for each mode is shown on the other table printed on
the bottom of the evaluation board, as shown in
Figure 6 on
page 7.
11. For I
2
C/SMBUS and DPST mode, connect the I
2
C interface
board to the ISL78171EVAL1Z board.
2
15. The LED current can be programmed by varying POT R
A1
using
Equation 1:
ILED
=
410.5
R
A1
+
R
16
=
410.5
R
13
(EQ. 1)
The measured current divided by six is the LED current per
channel. For example, 120mA measured current will correspond
to 20mA/channel.
16. The PWM dimming frequency can be adjusted by varying pot
R
A2
using
Equation 2:
F
PWM
=
6.66
10
R
A2
+
R
12
7
(EQ. 2)
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User Guide 035
V
IN
= 4.5V TO 26.5V
L=15
u
H
SCHOTTKY
DIODE, 60V, 3A
40V, 6 x 50mA*
V
IN
EN
FAULT
LX
ISL78171
VDC
REG
OSC AND
RAMP
COMP
FPWM
LED PWM
CONTROL
FAULT/STATUS
REGISTER
OVP
OVP
=0
IMAX ILIMIT
LOGIC
FET
DRIVER
PGND
COMP
CH0
GM
AMP
REFERENCE
GENERATOR
HIGHEST VF
STRING
DETECT
+
-
OC, SC
DETECT
OC, SC
DETECT
FAULT/STATUS
REGISTER
TEMP
SENSOR
SMBUS/I
2
C
INTERFACE
AND PWM
CONTROL
LOGIC
REGISTERS
PWM BRIGHTNESS CONTROL
DEVICE CONTROL
FAULT/STATUS
IDENTIFICATION
DC BRIGHTNESS CONTROL
CONFIGURATION
+
-
PWM/OC/SC
DC
FAULT/STATUS
REGISTER
CH5
*V
IN
> 12V
RSET
AGND
+
-
SMBCLK/SCL
SMBDAT/SDA
PWM
FIGURE 2. ISL78171 BLOCK DIAGRAM
PCB Layout Recommendation
The PCB layout is very important for normal functioning of the
ISL78171, to ensure the system works with low EMI. The main
power loop is composed of the input capacitor, boost inductor,
the output capacitor, the LX pin and the PGND pin. It is necessary
to make the power loop as small as possible and the connecting
traces among them should be direct, short and wide. The
switching node of the boost converter (LX pins) and the traces
connected to the node are noisy, so keep the low level signals
away from these noisy traces. The input capacitor should be
placed as close as possible to the VIN and GND pins. The ground
of input and output capacitors should be connected as close as
possible. The heat of the IC is mainly dissipated through the
thermal pad. Maximizing the copper area connected to the
thermal pad is preferable. In addition, a solid ground plane is
helpful for better EMI performance. It is recommended to add at
least 6 vias ground connection within the pad for the best
thermal conduction. Keep the PGND plane and AGND plane
separate and connect them at the thermal pad.
EMI Considerations
The LX node switches at the VIN potential so its capacitance to
GND should be made minimized. This is achieved by keeping the
LX copper island as small as possible and by opening the copper
GND area directly below it. This prevents injection of the
switching frequency noise directly into the GND, and reduces the
conducted EMI for the system. The evaluation board also has an
input LC filter option on it ie., L2/L2A and C
23
. These
components are not populated on the PCB but can be soldered in
for the purpose of EMI evaluation if needed. The snubber R
3
and
C
21
helps to reduce the peak voltage seen on the LX pin.
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